2nd Generation Specific 1986-1992 Discussion

Boost Dropping

Old 02-23-2005, 09:05 PM
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I drive a 90 TII that is COMPLETELY stock.. except for a RB catback exhaust. I can drive it for ~10 minutes and it boosts great to 8.6psi like it should, but after a little bit, it drops back down to 5.5psi. As I understand it, the stock EBC is supposed to raise it to the 8.6psi. What could be causing it not to go up properly?



Note: New plugs, fuel filter, voltage to fuel pump is perfect, clean oil.
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Old 02-23-2005, 10:26 PM
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maybe the boost solenoid is intermittanly not working? or the line is clogged?
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Old 02-24-2005, 07:32 AM
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Maybe IC heat soak?

To test, after boost falls off, spray some cold water on the IC & do another run.
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Old 02-24-2005, 09:40 AM
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Originally Posted by sureshot' date='Feb 24 2005, 05:32 AM
Maybe IC heat soak?

To test, after boost falls off, spray some cold water on the IC & do another run.

going out to test these two theories... gonna test the EBC with an Ohmmeter and then warm it up... til it won't boost anymore... then I'll check it with the EBC again and spray some water on the IC... or snow, since there's so much of it now
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Old 03-02-2005, 09:10 AM
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I haven't checked the EBC yet, but i went out yesterday in subfreezing weather with my car. It stopped boosting up to 8.6psi and i pulled over and drizzled snow on the TMIC... lots of dry snow. Some melted but the IC wasn't even hot to the touch. After that, it still wouldn't boost past 5.5psi.



I noticed my stock boost gauge reads low (doesn't zero when the car is in the on position). IIRC, that's controlled by the pressure sensor. Maybe that thing is acting up? Maybe it's the EBC? What else should I test?
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Old 03-03-2005, 12:50 PM
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Ahh man please dont rely on the stock boost gauge, like Ive said before all that thing is for is to know when at full boost and when ur not. Kinda like a turbo on and off switch.
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Old 03-03-2005, 01:31 PM
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I have an aftermarket gauge... don't worry. I just know that the stock boost gauge is controlled by the pressure sensor. I figured if that's screwing up, it could also be screwing other stuff up...
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Old 03-04-2005, 07:55 AM
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Originally Posted by JackoliciousLegs' date='Mar 3 2005, 11:31 AM
I have an aftermarket gauge... don't worry. I just know that the stock boost gauge is controlled by the pressure sensor. I figured if that's screwing up, it could also be screwing other stuff up...



I have seen my stock boost gauge work, work with low readings, & fail at various times.

All along the S-AFC's signal from the pressure sensor was perfect according to the mechanical boost gauge.

The problem seems to be between the dash gauge & the ECU.



The signal to the ECU has never been a problem.
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Old 03-17-2005, 03:46 PM
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Ok, just did a couple checks.



1. Stock EBC

I checked the resistance as per the FSM, and it's a solid 32 ohms... perfect



2. Pressure Sensor

5V to terminal w/ pressure sensor removed



2V read with no vacuum applied. on terminal D

0V with vacuum applied on terminal D



FSM says it should be reading 2V at 2psi vacuum. It read that w/o vacuum and read 0 with vacuum applied. Could this be the cause of my 5.5psi problem?
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